US vs. EU method for dust collector CFM?

[jrista]

I'm working on buying a dust collector for my shop. I have an overhead air filter, and a shop vac, but these have been woefully insufficient to really take care of the dust. My shop has been accumulating an amount of settled dust for a couple of years or so now, and that layer seems to be persistent. I vacuum up dust on the floor, but there is just dust on EVERYTHING, and cleaning all of that up has been really hard. I blow it off, and the overhead filter sucks up some of it, but most re-settles. I have a notable allergy to wood dust, so taking care of this has become top priority for this year as I get back into woodturning.

Most of my shop is Jet/Powermatic now, and Jet has a sale. I've been looking at this 2HP dust collector. From my research, for my shop size and my plans for a primarily 6" ducting, I'm calculating that I need about 4500fpm airflow. The CFM required to sustain that depends on the inlet size, and for 4" inlets I think I'll be fine, however I am not as sure for 6". However, I'm rather confused about all the reported specs for this particular model, as I've seen the CFM listed at around 930, 1200, and over 1500 CFM. Its the exact same model, so it is strange that its CFM is reported so many different ways. I can't quite figure out what inlet size these values are reported for, whether they are the "US" method or the "EU" method. I found this blurb in the documentation PDF for this particular collector as well, which reports both US and EU methods, but it doesn't really explain what those are, or why the results are different:

The 930 CFM is the main number I'm wondering about. A 4700+ FPM rating would be satisfactory, as I'd need 4500 for 6" ducting (will be starting with some flexible ducting, but longer term the intention is to add 6" metal ducting to the areas that need dust collection, then use the flexible ducting to actually connect each machine to that ducting.) I've worked out most of the connectors and splitters, will generally be using 45 degree splitters in most cases, except for a couple cases where, one way or another, 90 degrees is going to be required (and as I understand it, two 45s is the same as one 90 as far as how it impacts airflow).

My shop is narrow, but long, and I've only got one spot at one end where I could fit a DC. So, I'm going to have 6" ducting overhead down basically the middle of the shop, with splits off where I need to connect to each machine (and I've got 6 total right now, with a 7 that should be added later in the year). So...I need to make sure that I can maintain the necessary airflow to avoid chips and dust filling up my ducting over the entire length, and 4500 FPM seems to be the lower limit for my needs. But, I am honestly not sure if the above listed FPM is for...a 6" inlet, or 4" inlet? I am not sure what the US vs. EU method means, or which one may apply when? Is the 4763FPM listed here, actually what I'd be getting once I've installed the system and put in all the necessary ducting?

 

[jttheclockman]

You live in the US so I would concentrate on US values. Here are some links to past threads. There was a moderator here and is the owner of the Cactus juice stuff. He did a whole thread and write up on dust collecting when Curtis was still here He shown his shop with his duct layout. Trace him down here and read his posts. I am sure if you do a search he would be easy to find. What you ask is more complicated than just picking pipe size and duct size. Tool size is a huge factor. Length is a factor. Going up and down are factors. PVC and metal pipe are factors. Shutting of gates are factors. Branching off is a factor. Just remember dust collection is a small part of cleanliness in the shop. Dust collecting and chip collecting are two different things. To really collect dust at the source you need to have the tools enclosed and also collect dust at the cutting source. many times hard to do. Wish you luck. Anything is better than nothing.

https://www.penturners.org/threads/ordered-a-new-dust-collector-need-pipe-advice.105968/

https://www.penturners.org/threads/whats-the-best-dc-ducting-for-a-permanent-setup.49308/

More reading
https://www.woodmagazine.com/workshop/dust-collection/plan-a-whole-shop-dust-collection-system#:~:text=Plan a Whole-shop Dust-collection System 1 Start with,Super suction moves lots of air fast

 

[maxwell_smart007]

I thought that in the EU test method there is no dust filter connected to the machine - but that contradicts what your chart shows. Odd.

 

[jrista]

You live in the US so I would concentrate on US values. Here are some links to past threads. There was a moderator here and is the owner of the Cactus juice stuff. He did a whole thread and write up on dust collecting when Curtis was still here He shown his shop with his duct layout. Trace him down here and read his posts. I am sure if you do a search he would be easy to find. What you ask is more complicated than just picking pipe size and duct size. Tool size is a huge factor. Length is a factor. Going up and down are factors. PVC and metal pipe are factors. Shutting of gates are factors. Branching off is a factor. Just remember dust collection is a small part of cleanliness in the shop. Dust collecting and chip collecting are two different things. To really collect dust at the source you need to have the tools enclosed and also collect dust at the cutting source. many times hard to do. Wish you luck. Anything is better than nothing.

https://www.penturners.org/threads/ordered-a-new-dust-collector-need-pipe-advice.105968/

https://www.penturners.org/threads/whats-the-best-dc-ducting-for-a-permanent-setup.49308/

More reading
https://www.woodmagazine.com/workshop/dust-collection/plan-a-whole-shop-dust-collection-system#:~:text=Plan a Whole-shop Dust-collection System 1 Start with,Super suction moves lots of air fast

These are useful links, thanks. They do cover information I already know, generally...about duct sizing, inlet sizing, airflow, CFM for a given inlet size, etc. I'll be going through them in more detail later, to make sure I haven't missed anything in my planning.

The problem I am having is, for this one single DC unit, the JCDC-2, a 2HP unit, I have found the CFM listed at least three different ways, in different contexts. Some list it at 930CFM, some ~1200CFM, some over 1500CFM. Most of what I've read, says I need 1200CFM at least, for a shop my size with 6" ducting and a smallest inlet size of 4".

My problem is, I just don't know the CFM of the unit. In fact, I don't really know the CFM of any of the three Jet units in the lineup, which are 1.5HP, 2HP, and 3HP. Further, the CFM of the 3HP unit in the documentation is listed higher than that of the 2HP unit, but with a lot less airflow (lower than what is recommended for what I'll need to be doing for my shop.) The 2HP unit is a bit over 1200 CFM, at least according to the documentation file. According to a comparison table I was looking at in the local woodcraft, however, its listed as having a significantly higher at around 1900CFM. This table was an official Jet informational card. At that CFM, the airflow would be a lot higher. So, all of this inconsistency has left me confused as to the actual performance of each machine.

I think the JCDC-3, the 3HP model, is going to be too powerful for my use case, which isn't any better really than being underpowered. The JCDC-2 2HP model seems to be the right fit, I think...I'm just not sure. I honestly cannot tell if its a 930CFM, or ~1240CFM, or ~1530CFM unit. I suspect part of the discrepancy has to do with the inlet or ducting size used for the test, but I haven't actually seen that specified in the specs. Some people say that nothing less than a 3HP unit will do, however Jet's JCDC-3 is designed for 8" ducting to keep the airflow up, and I just can't afford that more expensive unit AND the larger ducting throughout my entire shop (metal ducting is 'SPENSIVE!!!!)

Anyway...just trying to understand the specs, make sure I don't buy an undersized unit, or one that cannot deliver the airflow I need... Seems very odd that the larger unit would have lower airflow, that doesn't make sense, but, I also don't entirely understand how they arrive at their numbers, so its all confusing.

I found some uncertain information, including Maxwell's here, that the EU method is simply without a filter. No one seems to know for sure, though...

I thought that in the EU test method there is no dust filter connected to the machine - but that contradicts what your chart shows. Odd.

Honestly not sure how useful that is...to test without a filter.

 

[jrista]

Ok, found an answer:

Dust Collector - 3 HP Cyclone Fan Performance Curve

www.lumberjocks.com

According to this post, the guy called Jet, and they said the EU method is without a filter. IMO that is pretty useless, so going with the US method. I also found some other info that cleared up the CFM/FPM testing. Its done at the maximum inlet size, so on the 2HP unit that's 6". So this unit should be able to deliver 936CFM @ 4763FPM with the 6" inlet. That'll work for my needs.

Guess that also means, the 3HP unit is tested at 8" inlet. So its 1240CFM @ 3542FPM is actually a huge amount of airflow, since its moving that fast through an 8" diameter pipe. The airflow (FPM) at 6" should be quite a bit higher.

 

[rixstix]

Not a dust collector guru here but...

Without a filter makes sense when you discharge through the wall to the outside world so that the 'fines' that cannot be caught by the filter don't settle inside the room. You get the full effect of the DC.

Marketing departments like to publish "best case" conditions which would be with a new, clean filter of the largest micron size possible.

 

[Curly]

You have probably seen the site Bill Pentz has but a lengthy detailed read over a number of nights should clarify some of your questions. Briefly some of the highlights.

You need a large volume of air to capture the invisible dust, under 10 microns, which are bad for your health. Bill concluded you need a minimum of 800CFM at the machine making the dust. A 4" duct can flow a maximum of 425CFM to 450CFM no mater what High Volume Low Pressure (HVLP) dust collector you connect to. The wall surface area to cross section area ratio is the restriction. A 5" duct can flow about maximum of 800CFM and a 6" duct flows about 1200CFM to 1250CFM. Flex hose has roughly 3 times the drag as smooth ducting (10' of flex has the same drag as 30' of smooth) so keep your use of it to a minimum. Best practice is to run 6" duct if the DC is capable to the machine and open the port to take the 6" and to ensure the openings into the machine are two to three times the size of the outlet duct to allow the air to flow freely. Unfortunately people don't want to cut up their machines to improve them.

The pair of 45º fittings in a duct being better than a singe 90º fitting is not always the case. If the 90º fitting has a bend radius of 1.5 or more it has less drag than the pair of 45º fittings. If you look at page 54 you will see the loss in feet of equivalent straight duct for each type of fitting with differing bend radii. You'll see that a pair of 45ºs plus the length of the straight in between has more drag than a larger radius 90º fitting. Best being a smooth 90º like you get with a Norfab stamped and welded seam system or a PVC duct being almost the same as the single 45º.

Here is a duct friction loss calculator you might find handy for doing "what if" calculations for comparisons. It doesn't allow for multiple sizes or duct materials so you will need to do each portion separately and add them up for a total. When the duct static pressure losses exceed the ability of dust collector to keep up you have dust escaping.

Unless your distances between machine and dust collector are short you may find a 2hp machine won't be enough. I know 3 guys with 3hp cyclones. 2 Laguna and one King. The guy with the King is happy with his because he is using large ducts over a short distance. Both guys with the Laguna are not happy because they are not getting the dust and the filters are clogging too fast. The reason is because both are using 4" ducts which are not capturing the dust where it is made and the second reason is the 4" duct doesn't allow enough air through the cyclone to separate the dust so it bypasses to the filter.

 

[jrista]

Not a dust collector guru here but...

Without a filter makes sense when you discharge through the wall to the outside world so that the 'fines' that cannot be caught by the filter don't settle inside the room. You get the full effect of the DC.

Marketing departments like to publish "best case" conditions which would be with a new, clean filter of the largest micron size possible.

So...to make sure I understand. You are just discharging wood dust into the atmosphere around your house? Wouldn't it settle outside, make a mess outside?

 

[rixstix]

So...to make sure I understand. You are just discharging wood dust into the atmosphere around your house? Wouldn't it settle outside, make a mess outside?

I used a chip cyclone to catch the bulk & never saw an issue with the fines.

 

[Curly]

So...to make sure I understand. You are just discharging wood dust into the atmosphere around your house? Wouldn't it settle outside, make a mess outside?

Most of the ClearVue Cyclones in Australia were sold without filters. They exhausted outdoors or had the cyclone outside doing the same. The particles from those cyclones are about 2 micron and smaller so it rapidly dissipates harmlessly into the background. If you can put a wye after the cyclone and switch from filters to outside discharge when it becomes warm enough and back again when it gets too cold.

 

[jrista]

You have probably seen the site Bill Pentz has but a lengthy detailed read over a number of nights should clarify some of your questions. Briefly some of the highlights.

You need a large volume of air to capture the invisible dust, under 10 microns, which are bad for your health. Bill concluded you need a minimum of 800CFM at the machine making the dust. A 4" duct can flow a maximum of 425CFM to 450CFM no mater what High Volume Low Pressure (HVLP) dust collector you connect to. The wall surface area to cross section area ratio is the restriction. A 5" duct can flow about maximum of 800CFM and a 6" duct flows about 1200CFM to 1250CFM. Flex hose has roughly 3 times the drag as smooth ducting (10' of flex has the same drag as 30' of smooth) so keep your use of it to a minimum. Best practice is to run 6" duct if the DC is capable to the machine and open the port to take the 6" and to ensure the openings into the machine are two to three times the size of the outlet duct to allow the air to flow freely. Unfortunately people don't want to cut up their machines to improve them.

The pair of 45º fittings in a duct being better than a singe 90º fitting is not always the case. If the 90º fitting has a bend radius of 1.5 or more it has less drag than the pair of 45º fittings. If you look at page 54 you will see the loss in feet of equivalent straight duct for each type of fitting with differing bend radii. You'll see that a pair of 45ºs plus the length of the straight in between has more drag than a larger radius 90º fitting. Best being a smooth 90º like you get with a Norfab stamped and welded seam system or a PVC duct being almost the same as the single 45º.

Here is a duct friction loss calculator you might find handy for doing "what if" calculations for comparisons. It doesn't allow for multiple sizes or duct materials so you will need to do each portion separately and add them up for a total. When the duct static pressure losses exceed the ability of dust collector to keep up you have dust escaping.

Unless your distances between machine and dust collector are short you may find a 2hp machine won't be enough. I know 3 guys with 3hp cyclones. 2 Laguna and one King. The guy with the King is happy with his because he is using large ducts over a short distance. Both guys with the Laguna are not happy because they are not getting the dust and the filters are clogging too fast. The reason is because both are using 4" ducts which are not capturing the dust where it is made and the second reason is the 4" duct doesn't allow enough air through the cyclone to separate the dust so it bypasses to the filter.

Thanks for the resources. Checking them out now.

So, I've found a number of tables that I've been using to determine CFM at the inlet. For 6", I've never seen 1200-1250 listed. Usually its around 900 to maybe 1000 CFM. But I don't think it is just as simple as that, as what your CFM is is related to both the duct size, and the airflow (FPM), from what I understand. And it looks like dust collectors can range anywhere from 3500 to 5000+ FPM, depending on the design, primary duct size, HP, etc.

The Jet I'm looking at, is over 4700 FPM at 938 CFM, through a 6" port (at least, according to their specs). My goal is to run 6" ducting as far as I can and as close to each machine as I can. Then I'll be using flex tube just to connect the ducting to a port near the machine (i.e. my big lathe has this large port attachment and adjustment system so I can flexibly position the port wherever I need to.) The big powermatic will use a 6" port, so it should be 6" through and through. My small lathe will use a 4" duct most likely. I have a bandsaw with two 4" ports, which I intend to split off of a 6" duct as close to the machine as possible. I am not sure how long the flex hose will need to be, though, as depending on what I'm cutting and how long, I'll move the bandsaw around (its on a wheely base), so I need some flexibility there. Hopefully I won't need more than maybe 3 feet each for a pair of 4" flex hose though.

I actually never said that 45 was better. What I've read is that a pair of 45s is usually NO better than a single 90, and if you just need a 90 degree turn, then a single 90 will do just as well as two 45s. So what you are saying here seems to corroborate that, and potentially indicates that a single 90 might actually be better, as long as it has a large enough radius? I intend to use metal, unless it just comes out to be too darn expensive. I'm worried about static buildup with PCV. I have a nat gas pipe that runs high up along one of my walls. Its mostly covered by wood to protect it, but there is a run that is exposed (which I'm trying to figure out if I can cover that as well.) Still, static discharge worries me. I intend to keep all ducting as far away from that as I can, but and electrical field can move around say a wood physical protective barrier, so I dunno... Maybe there is an ingenious way of grounding PVC ducting that will completely alleviate that issue?

Regarding distance...my shop is about 11 feet wide, but more around 26 feet long or so. So the DC will be at one end, I'm going to run 6" ducting up, then ideally strait down the center of my ceiling to the other end. So I can drop 6" ducting right down to each machine, all of which are arrayed down that length. One machine that will be done a little differently is my main lathe, where I'll run 6" ducting off a 45 degree branch, strait off the outlet pipe from the DC. So this main lathe, will get a short run of strait 6" ducting, then that will connect with a very short piece of flex hose to probably a bellmouthe hood at the lathe. So this should have the most power, and will be one of the most used machines. The others, I'll have to run ducting up, down the center of my ceiling, then drop off branches to each machine, all of which are arrayed along the sides of my shop. Now, I sadly don't really have the opportunity to arrange my machines so that those that need the most sucking power are closest to the DC. Some of them just because of the space I have, are at the opposite end. Eventually a table saw will be down there as well.

So...I dunno. I guess the ducting will probably be more like 22 feet long (plus I guess, any rise from the DC inlet, to the ceiling...I guess that is about 10 feet or thereabouts, maybe a little less depending on how high off the ground the inlet is), as the DC is not all the way at the very other end...its up by...maybe 3 feet or so from the other end. I'll have to see what friction loss is going to be like over 22 feet. I thought I'd determined that the 2HP would work... I guess I could also get clever with exactly how I run the ducting. I could probably rotate the 90 degree at the top of this vertical rise, at a 45 degree angle, run a length at 45 degrees to the center, have a 45 degree angle connector that I can run the main line down the rest of the garage, then branch off of that as necessary. That might allow me to replace a 90 with a 45.

A problem I have is that, I don't think I really have room for the 3HP. That sucker is like 78" tall, and I have a manual garage door in this part of my garage that I still need to be able to open. I think I might have maybe 2" of clearance, but its pretty darn tight. The 3HP also has a larger footprint, that i'm not sure I can actually fit into the space I have, in that corner of the shop. Not a whole lot of options, either, as I have to run a 240V outlet, and there aren't many places I can put that either...in fact, this is really the only corner of the shop that I can. This is one of the main reasons I haven't been considering the 3HP model. Just not sure I can make it fit and work. However, if 2HP is just not going to be enough......

 

[jrista]

Running the pressure loss calculator, just for the main line, to the other end of the shop, for the bandsaw (without accounting for any flex hose to connect that ducting to my 4" ports):

Total Duct Loss (inches Water): 4.218

Honestly not quite sure how to evaluate that...what is the expected loss in inches of water for normal use? Is 4.2" too much, in line with expectations?

 

[jrista]

Ok. So, I think I get where people get their "you can get no more than X CFM through a Y duct diameter" stuff. Its based on FPM assumptions. It seems the 785CFM is strictly based on a 4000 FPM airflow. If you have higher or lower airflow, then your maximum CFM would be affected. I've found so many tables that give CFM ratings for different duct diameters, and they all seem to give different figures. I guess everyone assumes a different baseline for airflow in FPM. Given duct loses themselves, that makes it a much more complicated problem, as if your FPM at the point where you switch to flex hose or whatever to connect to an actual at-machine hood or a machine port is lower than the, say, 4700+ FPM rating of the machine, then that would certainly affect the CFM you are pulling right at the machine.

 

[Curly]

If you look at the figures in your original post the maximum flow is with 2.5" of H2O. That is not enough to overcome the 4.2" of loss in your rough calculation. Your flow will drop a lot therefore the need for a bigger DC.

The static pressure is an important factor. With a given duct diameter the higher static pressure, the lower the flow. Conversely the lower the static pressure the higher the flow. A motor and impeller can only pull so much. What Jet should give you is a fan curve showing the relationship of the two. I'll attach a set of fan curves I saved from ClearVue a long time ago. You will see how they effect each other.

 

[jttheclockman]

http://billpentz.com/woodworking/cyclone/index.php

 

[jrista]

If you look at the figures in your original post the maximum flow is with 2.5" of H2O. That is not enough to overcome the 4.2" of loss in your rough calculation. Your flow will drop a lot therefore the need for a bigger DC.

The static pressure is an important factor. With a given duct diameter the higher static pressure, the lower the flow. Conversely the lower the static pressure the higher the flow. A motor and impeller can only pull so much. What Jet should give you is a fan curve showing the relationship of the two. I'll attach a set of fan curves I saved from ClearVue a long time ago. You will see how they effect each other.

I'm confused here. The specs state that the maximum static pressure loss is 10" of water column... Wouldn't that support a 4.2" drop over the max distance? How could ANY DC system today, only support 2.5" of WC loss...that wouldn't support anything. I've found people using the JCDC-2 for much larger workshops than mine...

Remember, the maximum flow they state in their specs, is just with the default 6" port. I don't believe there is any ducting or anything else attached.

 

[Curly]

The 10" is with no air flow (duct blocked off). Wide open it is 2.5". Look at the fan curve in post 14. It shows maximum flows at 2" of static pressure. At 16" of static the airflow is around 400CFM almost blocked off. The middle ground has flows of 1200CFM with 8" of static pressure. That can easily overcome the static pressure loss of your rough calculation. The CVs have a 5hp motor and bigger impeller verses the 2hp you are considering. A 3hp might have enough flow and static pressure as long as the impeller is bigger than the 2 hp. I say that because many of the 2hp bagger DCs have a 12" impeller and the same companies have 3hp DCs with the same 12" impeller. The only reason they flow more is the extra filters allow more flow. You can't trust most manufacturers to give accurate data because they would all be about the same for any given size DC not leaving much to differentiate themselves from the next. They cherry pick and embellish.

The standard way of testing an impeller is without any filters, just a short test duct and a single measurement in the middle of the airstream where it is fastest. Not sure how they test one with the cyclone and impeller together.

People may be using 2hp for bigger shops and might even claim great flow tests but they are either guessing how great they are working or test with a fan type anemometer which are not suited for testing flows in small ducts. The air has to speed up to get around and through the fan and housing so the readings may be as much as 50% higher than actual. They should be using a test duct and either a thermal (hot wire) anemometer or a pitot static anemometer and take a number of readings across the diameter of the duct and averaging them. Usually eight readings.

I will suggest again you read Bill Pentz's site I linked above. It is a hard long read with lots of repetition (partly because people come in a read a section or two without getting all the info). I have read it a few times end to end over the years and it never gets easy but it has good information.

Ultimately you will have to decide what to get based on who you believe, you space requirements and your budget. It's your health and it important enough to get it right for your circumstances.

 

[jrista]

The 10" is with no air flow (duct blocked off). Wide open it is 2.5". Look at the fan curve in post 14. It shows maximum flows at 2" of static pressure. At 16" of static the airflow is around 400CFM almost blocked off. The middle ground has flows of 1200CFM with 8" of static pressure. That can easily overcome the static pressure loss of your rough calculation. The CVs have a 5hp motor and bigger impeller verses the 2hp you are considering. A 3hp might have enough flow and static pressure as long as the impeller is bigger than the 2 hp. I say that because many of the 2hp bagger DCs have a 12" impeller and the same companies have 3hp DCs with the same 12" impeller. The only reason they flow more is the extra filters allow more flow. You can't trust most manufacturers to give accurate data because they would all be about the same for any given size DC not leaving much to differentiate themselves from the next. They cherry pick and embellish.

The standard way of testing an impeller is without any filters, just a short test duct and a single measurement in the middle of the airstream where it is fastest. Not sure how they test one with the cyclone and impeller together.

People may be using 2hp for bigger shops and might even claim great flow tests but they are either guessing how great they are working or test with a fan type anemometer which are not suited for testing flows in small ducts. The air has to speed up to get around and through the fan and housing so the readings may be as much as 50% higher than actual. They should be using a test duct and either a thermal (hot wire) anemometer or a pitot static anemometer and take a number of readings across the diameter of the duct and averaging them. Usually eight readings.

I will suggest again you read Bill Pentz's site I linked above. It is a hard long read with lots of repetition (partly because people come in a read a section or two without getting all the info). I have read it a few times end to end over the years and it never gets easy but it has good information.

Ultimately you will have to decide what to get based on who you believe, you space requirements and your budget. It's your health and it important enough to get it right for your circumstances.

Thanks for the info and insights, Pete. I'm holding off for now, and am reading Bill's entire site.

 

[jrista]

The 10" is with no air flow (duct blocked off). Wide open it is 2.5". Look at the fan curve in post 14. It shows maximum flows at 2" of static pressure. At 16" of static the airflow is around 400CFM almost blocked off. The middle ground has flows of 1200CFM with 8" of static pressure. That can easily overcome the static pressure loss of your rough calculation. The CVs have a 5hp motor and bigger impeller verses the 2hp you are considering. A 3hp might have enough flow and static pressure as long as the impeller is bigger than the 2 hp. I say that because many of the 2hp bagger DCs have a 12" impeller and the same companies have 3hp DCs with the same 12" impeller. The only reason they flow more is the extra filters allow more flow. You can't trust most manufacturers to give accurate data because they would all be about the same for any given size DC not leaving much to differentiate themselves from the next. They cherry pick and embellish.

Since you have one of these CV DCs. Do you know what the dimensions are? I am not finding those details on the web site. This system would certainly be more expensive, but...I am amazed at the 99.999% of 0.5 micron or larger particle filtration. This is something I've been reading, that many DCs will just pump fine wood dust back into the environment. I have an overhead air filter that should take care of some of that...but still, for a filter that claims to be 1 micron, that is still pumping dust back into the environment... This is my health, and it does matter to me. So, I'm willing to invest more money if that's what it takes to preserve my health.

 

[Curly]

From your post 11.
"I intend to use metal, unless it just comes out to be too darn expensive. I'm worried about static buildup with PCV. I have a nat gas pipe that runs high up along one of my walls. Its mostly covered by wood to protect it, but there is a run that is exposed (which I'm trying to figure out if I can cover that as well.) Still, static discharge worries me. I intend to keep all ducting as far away from that as I can, but and electrical field can move around say a wood physical protective barrier, so I dunno... Maybe there is an ingenious way of grounding PVC ducting that will completely alleviate that issue?"

I was going to address and forgot. In a home shop sized system you can't generate a hot enough spark to ignite wood dust nor generate enough dust to ignite. Most collector fires are form sparks or embers ending up in the bin. Either metal picked up and hitting the impeller making a spark, not the case in a cyclone. Or an ember made when blades are dull or the wood pinches and the friction heats the wood enough. Table saws and router tables being most common.

The static from a duct is more of an annoyance when zapped, which could distract and be dangerous if sawing etc. It can also do damage to sensitive electronics, computers of CNC etc.

In your case a natural gas line is a different kettle of fish and it might be best to ask the appropriate people.

PVC is an insulator and doesn't lend itself to grounding. An explanation why.

I think you could surround a duct with fine wire mesh from end to end and ground it, like a Faraday cage, but that isn't very practical. What could work, I have yet to try it though, is a static dissipating finish. They are used in electronic rooms and benches to carry off static charges to protect sensitive computer boards. https://www.uline.ca/Product/Detail...Finish-1-Gallon-Bottle?keywords=static+finish There are other brands and sellers closer to you. I don't know if it would stick to PVC but if it did one could ground the system and eliminate the nuisance sparks and protect electronics if you have any. In this area large diameter PVC is hard to come by and costly so most people lean towards spiral metal ducting.

CV size.
Look at the instruction manual of the cyclone you are considering and the dimensions are a few pages in.

Assembly Manuals & Instructional Videos for Clear Vue Cyclones

Find the Manuals and Instructional videos to help walk you through the use and assembly of your Clear Vue and Pentz Dust Collection System.

www.clearvuecyclones.com

Edited to add.
The cyclone can be tilted/leaned over to reduce the headroom needed. You can put shelves and storage over and under it to minimize the extra wall space needed. Here is and old Fine Woodworking thread post show a drawing of it. A Canadian recently set his up that way and says it is working as well as it did in the last shop he had it in.

 

[jrista]

PVC is an insulator and doesn't lend itself to grounding. An explanation why.

Hmm. I feel this "test" was flawed, as he only tested a small segment of PCV pipe, and without any static charge built up on it at that. When a static charge builds up on the surface of PCV, it is not the PCV that conducts...it is the built up charge itself, thanks to the electric field that charge creates, that actually conducts (once that field reaches something that can conduct it to ground).

I wish this guy had actually tested the resistance of PCV ducting that actually had static charge already built up on it. If he had, I believe his results, and the measured resistance, would have been significantly different. Draining the charge is the point...it doesn't matter that PVC itself isn't conductive.

Further, I believe to actually solve the static charge buildup problem, grounding the outside of the ducting wouldn't be very effective...you would have to ground the inside. Hence why I was wondering if anyone had an ingenious way of doing that. Your recommendation of using a static dissipating coating on the pipe is actually pretty ingenious, I have to say. If you could coat the inside of the pipe, then maybe have metal grounding points periodically...that might actually work...

 

[jrista]

"They found to get good fine dust collection at stationary small shop tools we need to move air at close to 4000 FPM with a volume of no less than 1000 CFM using at least 7 inch diameter ducting."

So, does this mean that a 6" duct is simply not sufficient to move fine dust?

 

[Curly]

The 7" is ideal but as it isn't common in PVC so people use the 6", going to 8" will slow down the airspeed, possibly to the point of heavier dust dropping out and settling in the duct. The people selling spiral in any given city can make any size including 7" along with any fitting radius or configuration you need.

 

[jrista]

The 7" is ideal but as it isn't common in PVC so people use the 6", going to 8" will slow down the airspeed, possibly to the point of heavier dust dropping out and settling in the duct. The people selling spiral in any given city can make any size including 7" along with any fitting radius or configuration you need.

Using the CV spreadsheet calculator, 8" won't do with anything I could afford right now. Even with the CV1700, things are way beyond my original budget already, and it looks like even a 7" pipe has too low airflow. A 6" pipe would have enough airflow, but when I toss in even just a couple of 2.0 R/D 90s and a couple wyes, the SP loss is over 18" WC. So its a bust. At least, that is, if I want 1000CFM at the machine, I guess...

I'm not sure how anyone is able to get sufficient dust collection with any system on the market now, considering all the losses each system would have. I've been reviewing systems with 50 feed of overhead ducting, with more machines attached than I have so may wyes, numerous 45 degree and usually several 90 degree angles. The machines at the end of the run, would have maybe 350CFM. So, these systems are only collecting chips, but aren't capturing all the fine dust?

EDIT:

I may have had a miscalc before. There is an area for "trashcan separator", and since I was intending to use the barrel collector, i thought that is what that was for. I think, though, I misunderstood that, and it actually means a legit trashcan collector, which IIUC means just a trash can, two holes drilled in the lid, with one of them having some angled piping attached, which effectively creates a vortex to separate chips from dust. I remember reading about those a while back, and found several people saying they hurt airflow too much. Seems to be the case. Also seeing why people rave about Pentz cyclones, as they seem to impose the lowest WC hit compared to other cyclones, and certainly to a trash can separator.

So, correcting for this, I'm just about 12" WC in terms of SP loss. That would put the system at its limits...and, I'm not quite sure I've accounted for all the angles yet.

EDIT 2:

Just realized that, with the CV1700 design, the inlet is at the top of the system. That in fact, would eliminate the need for a couple of 90s, and if I am able to orient the system the way I want, I could pipe off the system at 45 degrees, have another 45 for the main pipe down the middle of my shop's ceiling. I'd then wye off for each machine, and have just ONE 90 at the walls. I also adjusted another spec, the filter loss, down from 0.5 (for a 225sqft) to 0.3 (300sqft) as the machine has a 300sqft filter by default. These reduced the SP loss to a little over 10", which is under the 12" they specify as the threshold for a larger machine.

 

[monophoto]

While it's probably interesting to debate the US method versus the EU method, the thing to remember is that they are simply different ways that the performance measurement can be conducted. The bottom line is that both sets of measurement apply to the same machine.

On the other hand, you said that you calculated that you "need about 4500fpm airflow." How did you do that calculation? More specifically, did the calculation method you used anticipate matching a dust collector rated to US or EU standards? If the method you used was based on the assumption of a US standard dust collectior then you should compare that calculated need with the US-standard ratings of the dust collectors you are considering.

 

[jrista]

While it's probably interesting to debate the US method versus the EU method, the thing to remember is that they are simply different ways that the performance measurement can be conducted. The bottom line is that both sets of measurement apply to the same machine.

On the other hand, you said that you calculated that you "need about 4500fpm airflow." How did you do that calculation? More specifically, did the calculation method you used anticipate matching a dust collector rated to US or EU standards? If the method you used was based on the assumption of a US standard dust collectior then you should compare that calculated need with the US-standard ratings of the dust collectors you are considering.

So, I guess it depends on whether you are talking horizontal or vertical airflow. As I understand it, vertical airflow must be 4500FPM in vertical branches, 4000FPM in the horizontal main, to be transported successfully. I've come across this in a few different places, however this is the only article I can find ATM that notes this (they say "branches", other articles were clearer that it was the vertical ducting airflow speed that needed to be 4500FPM):

https://www.spiralmfg.com/wp-content/uploads/2015/09/dust_collection.pdf

This isn't based on any particular dust collector. Its just what is necessary to transport all dust created, chips, fine dust and all, vertically. The 4000FPM spec is only for horizontal ducting, and is the minimum required to ensure that dust and chip particals don't fall and pile up on the bottom of the duct and create "damming" issues to the airflow. This difference in required airflow isn't talked about in most articles on dust collection, but I have found a few. I am not sure exactly what the formula is to calculate the figure myself...I've just been following what I've been finding so far.

The Bill Pentz site linked by a couple above, actually has this information detailed out fairly specifically somewhere. Not sure where it is ATM.

 

[Curly]

When you are doing your calculations are you using all the wyes and bends for the whole system of just where the air takes a turn? If I understand your layout there would be a straight duct from the cyclone inlet to the first 45º then straight through several wyes until the last 90º turning down to possibly a final 90º at the bottom by the floor or wall. You would only count the wyes the air flows through if changing direction. That straight to the end of the shop would roughly be 26' of pipe, 1of 45º elbow and 2 of 90º elbows. Using the calculator I linked with 6" duct and 1700CFM I got a loss of 7.288". Did the same using 7" and got 3.453" of loss. I didn't put in the filters. The CV comes with two filters of 300 sq ft each for a total of 600 sq ft making the filter losses negligible. Have I got it basically right or misunderstanding? Not the first time.

I don't use Bill's calculator because I have an old iMac and Libre Office Suite and they don't play well together.

 

[jrista]

When you are doing your calculations are you using all the wyes and bends for the whole system of just where the air takes a turn? If I understand your layout there would be a straight duct from the cyclone inlet to the first 45º then straight through several wyes until the last 90º turning down to possibly a final 90º at the bottom by the floor or wall. You would only count the wyes the air flows through if changing direction. That straight to the end of the shop would roughly be 26' of pipe, 1of 45º elbow and 2 of 90º elbows. Using the calculator I linked with 6" duct and 1700CFM I got a loss of 7.288". Did the same using 7" and got 3.453" of loss. I didn't put in the filters. The CV comes with two filters of 300 sq ft each for a total of 600 sq ft making the filter losses negligible. Have I got it basically right or misunderstanding? Not the first time.

I don't use Bill's calculator because I have an old iMac and Libre Office Suite and they don't play well together.

I've been focusing on the longest path, not every wye and turn in the system at large. I was also originally over-estimating the 90 degree turns, as I was still thinking about the need to raise the ducting to ceiling level (as would be necessary with the old system.) With the CV systems, I could simply mount them at the right height for the ducting AT ceiling level, which eliminates a couple of 90 degs. In fact, if I can orient the inlet of the CV collector itself, then I can eliminate everything at the top except the wyes, I think, and then have just one 90 deg turn at the walls.

I am having to reconsider the original layout, though. I don't think I have any room to install the DC in the original location due to the garage door, and all the infrastructure to support that. Since this is a wall mount unit, that opens up the possibility of mounting it on the opposite corner of the workshop, on an existing wall that has been drywalled already. I can mount it up the wall a ways, so it will sit above my air compressor. That completely changes the ducting situation, though...so, I'm trying to figure that out now. It may well be that if I end up with the CV system at the opposite corner of the workshop...then I'll probably just pull a strait pipe right out of that, then have one wye that drops down towards my lathe on one side of the shop along that run. Another wye would split, then turn 45, to take me strait out over to the other wall, which I would then drop down to the other machines. My bandsaw would be along the same wall as the CV system itself, so I'd wye off this tangential line and drop a duct right down to the bandsaw. The other wall is what I'm still working out. Overall, though...if I'm clever enough, I think the system would probably have just one, maybe two 90 degree turns in total, for any given path.

Now, I'm not quite sure I understand this notion about only counting the wyes if it changes direction? What exactly do you mean by change direction?

 

[jrista]

Hmm, another question. The CV systems make specific note of the fact that the filters are off of a 90 degree turn. I am not sure if that is something I need to account for, as another turn in the entire system? I am honestly not sure. On that side of the impeller, the pressure would be positive, rather than negative...but maybe that 90 degree turn still has an impact on the overall system?

 

[jttheclockman]

I really hate to tell you this but all those numbers are with a clean pipe run and brand new filters and clean dust collector and they all go out the window after a few months of use if you are a serious woodworker. Believe me. You will not collect the dust you are striving for as well as you may think. I give you credit for trying to put together the best system you can and afford. But you will never get all dust out of the air. You need to enclose your tools also. At every blade and every cutting tool dust will escape. Look at a tablesaw or a bandsaw and if you use zero clearance plates to avoid small pieces falling through you now have all dust coming off blade into air so you need to capture that at the source with some sort of dust collection. Dust does not stick to blade and get carried under the table top. Now you have to figure that into your calculations as well.

Another thing you need to consider is placement of dust collector and if you are enclosing in a room because it needs air flow. Each style collector has regulations on this also. I wish you the best of luck and hope you get things worked out so you can safely work and enjoy your shop.

https://www.woodmagazine.com/workshop/dust-collection/guide-to-workshop-dust-control

 

[jrista]

I really hate to tell you this but all those numbers are with a clean pipe run and brand new filters and clean dust collector and they all go out the window after a few months of use if you are a serious woodworker. Believe me. You will not collect the dust you are striving for as well as you may think. I give you credit for trying to put together the best system you can and afford. But you will never get all dust out of the air. You need to enclose your tools also. At every blade and every cutting tool dust will escape. Look at a tablesaw or a bandsaw and if you use zero clearance plates to avoid small pieces falling through you now have all dust coming off blade into air so you need to capture that at the source with some sort of dust collection. Dust does not stick to blade and get carried under the table top. Now you have to figure that into your calculations as well.

Another thing you need to consider is placement of dust collector and if you are enclosing in a room because it needs air flow. Each style collector has regulations on this also. I wish you the best of luck and hope you get things worked out so you can safely work and enjoy your shop.

https://www.woodmagazine.com/workshop/dust-collection/guide-to-workshop-dust-control

I am aware I won't be collecting 100% of the dust. That said, based on what I'm reading with Bill Peltz's site, if you want to collect the vast majority of it, then you need a system that has enough collection power (1000CFM at the point of collection), enough airflow to keep it all moving, and a filter that will avoid dumping a bunch of it back into the atmosphere. So far, Mr. Peltz site has been quite enlightening. I am clearly interested in building a "Fine Dust Collection" system, which is not what most dust collectors are really capable of, it sadly appears.

Even government agencies who oversee worker health like OSHA used to say except for Western red cedar all airborne wood dusts are only nuisance dusts that only cause minor irritation and stuffiness. Most small shop workers and hobbyists also assume we have minimal exposure because of our limited shop time. Many also see our hand tools make almost no visible dust so assume they make little to no dangerous fine dust. Most wrongly assume our collectors that can suck up a tape measure or other small tools should easily collect the fine dust we can blow around with the lightest breath. Most also now have finer filters on shop vacuums, air cleaners, dust collectors and cyclones that leave clean looking shops, so assume they have no fine dust problem, but testing shows almost all of these systems freely pass the unhealthiest fine dust. Sadly, as you will see if you keep reading all of these assumptions are wrong.

Cal OSHA testing shows most small shops that put and vent their dust collection systems inside have dangerously high levels of fugitive fine dust that previously escaped collection. The accumulated fine invisible dust is so built up in most small shops that just walking around without making any more dust stirs enough dust airborne to fail EPA air quality tests. Cal OSHA testing also shows a few hours in almost all shops that vent inside causes more fine dust exposure than full time large facility workers get in months. This should terrify small shop workers and hobbyists because the peer reviewed medical research clearly shows the higher and longer the exposure the greater the damage.

I can attest to this! I've had serious problems with fine dust! Its definitely hurting me.

The mid-level Jet, Powermatic, Laguna, etc. filters mostly don't capture dust small enough to start with. Most list a 1 micron filter, however that's sketchy to start with as most don't list much more than 90% capture at that level. Jet used to specify a 1 micron filter, but now they call it a 2 micron (or in one case even a 5 micron) filter, at 99%. Some of the newer Lagunas may be exceptions, listing 0.2-2 micron dust is captured at 99.7%...however, the fact that they list a range, makes me suspicious. Exactly how much 0.2 micron dust are they really capturing? I doubt 99.7%, and 2 micron is probably significantly better than 99.7%.

A 1 micron filter at 90% now simply seems insufficient and useless, if most of the fine dust is going to find its way back into the atmosphere. The goal here, really always was but I understand it better, is to make sure I'm minimizing the amount of fine, allergy-inducing dust that sticks around in the atmosphere. There isn't any point in a DC at all, unless it can do that. I also have the overhead air filter, which I always run for an hour or so after I leave the shop to clean up particulate that remains in the air. I also use a respirator while I am working. My biggest concern is when I'm out there for reasons other than woodworking, and may not have a respirator on. As it stands now, if I go out into my garage and do anything other than simply get in my car and drive off, I'm almost guaranteed to get some dust in my nose, and then its all over...for days, or even a week or more. My reactions to wood dust are pretty severe, and that probably has to do with the fact that I'm already allergic to tree pollen, plus some exposure I had during the early pandemic era (that was when I first started turning), when it was literally impossible to buy any kind of respirator, as they were ALL reserved for front line responders at the time. So, I suffered with simple and useless cloth face masks.

I can't keep getting exposed, and I need to make sure that I have effective ways to capture dust on creation, as well as clean it all up when I'm done (i.e. floor sweep inlets), and clear the air as well. Right now the air filter has pretty limited utility. There is so much dust in my garage already when I first start turning, and I produce so much while turning, the air is permeated with it after a little bit of blowing and sanding. The filters on the AFS don't take long these days to get clogged enough to reduce the effectiveness of the AFS even further. Its just a vicious cycle. My shop just keeps accumulating more and more dust, and I'm all but guaranteed to get some kind of exposure these days (usually when I', not actually woodworking, say just pulling the lawnmower out.) I basically have to wear a respirator any time I go out there to do anything, which is rather annoying, and even then, I still sometimes seem to get enough exposure that I'm back in respiratory distress within a day. I can't keep living like that. Its miserable.

So, if I am going to build a dust collection system, based on the link you yourself shared, then it sounds like I need a system capable of at least 1000CFM @ 4000/4500FPM (minimum), with 6" primary ducting. I know it won't capture every single particle of dust, but I'm quite sure it will have a dramatic impact on my overall dust problem, which right now is effectively uncontrolled. A system capable of doing this, however, is going to have to be quite a bit more capable than the dust collectors I've been looking at the last couple of weeks. Moving 1000CFM of air at the source, is a good deal more than moving 350-400CFM. I thought I could get away with around $2000 invested in the DC itself. Well, it seems I'm more likely going to have to spend around $3400 or more, to really get a system capable of sucking with enough. I guess, I'll have to consider the options for ducting. Might have to use PVC, if I can find a way to ground it. I've had some nasty shocks even just with the shop vac, enough to render my finger numb, then painful, for a good while. I hate that, at the very least, At the same time, its very dusty and dry in Colorado in general, and it seems static buildup is pretty easy here in general...and I just don't want to take any risks. I may have to come up with some kind of ingenious solution for static buildup myself. I've got some ideas rumbling after Pete mentioned that antistatic coating stuff...

I have no delusions of collecting every particle of dust. However, I DO expect that once I put thousands of dollars into a dust collection system, that it will actually be worth it at all. My original plan with metal ducting and a DC like the JCDC-2/3 from Jet, was actually still going to cost me around four grand anyway, accounting for all the metal ducting. I guess another $1200 or so, ain't all that big of a difference in the grand scheme of things, and maybe I can reduce the amount of metal ducting if I place the DC in a different location.

Regarding enclosing the DC. I'd like to, from a noise standpoint, for sure. Sadly, I don't have any way to do so, so for now, it will just be attached to the wall of the workshop itself. Shouldn't have any problems with return air or air pressure in a DC room.

 

[jttheclockman]

A way to look at things is if the dust collector has enough suction to collect large particles or chips it has enough power to collect whatever dust is present at the opening. Plain and simple. Your biggest dust producing tools is any sander weather a vertical or horizontal drum sander, portable sanders and the lathe where you sand. Now if you use your tablesaw as a sander than that too. When I was in my shop almost everyday and producing lots of dust and work pieces for my scrollsaw work I always tried and still do, to sand projects outdoors. Yes the drum sanders were a huge source of dust but I hooked up a shop vac directly to them with a heppa filter. Controlled those very well. My lathe has a dust hood and collects most dust when sanding small items such as pens. I had a better quality 1micron filter dust bag put on my dust collector. As I said all works great when new but my dust collector can hardly pick up wood chips from my jointer any more. You are constantly cleaning the gates. You need to empty the drum more often as well as dust bag because they do clog and now air efficiency is cut down. To me and this is just me. Get a good quality collector that can handle your needs and spend the money on another air cleaner. Calculating collection for each tool is so simple today with all these charts from various sources. Now the ratings on each tool collector is a manufacture thing and can it be trusted, well that falls under the same category when they rate their HP rating on motors. Every company has their method. Go to woodworking forums and talk it up there. See what others are using and make your choice off that first hand reports.

Now you mentioned a couple times about PVC and static and grounding. This is a debunked myth within a home workshop. You will not produce enough static within or outside a pvc pipe to cause a arc. In an industrial site where they run higher rpm machines and tools and more of them and move alot more air through their duct systems they use metal and still can get an arc and have had it happened even when grounded. PVC pipe is a nonconductive material so wrapping the pipe with copper wire as some people do and some even lay a wire inside the pipe to help combat static is pointless because static is only prevented where the wire makes contact with the pipe. Now I have seen some people wrap their pipes with aluminum duct tape. Now this is probably a more efficient way to avoid nuisance static on the outside of the pipe where you may touch it but does nothing to the inside because again pvc is a nonconductive material. Then you have the adhesive value of the tape and does it actually work, I do not know. Arcs mainly happen if when cutting you hit a piece of metal such as a nail or even cutting aluminum and chips that are hot can now contact wood chips or if these shards hit the impeller on the dust collector fan and land within the dust containers. That is how fires can start. This can happen when drill metals also and you suck up the filings through your dust collector. Keep the collector clean will help prevent this. Now they do make antistatic PVC pipe and also a coating that can be apllied. How expensive it is I do not know the particulars but imagine it is not cheap. To me and is what I did was to use metal air handling round duct. I grounded to a water line because my main water line is in my shop. To prove this point if you want, try wrapping your vac hose with copper wire and ground it. Run the vac and then touch the hose in any place there is no wire touching it and see if you get shocked.

Dust is a health problem and unless you can collect at the source it will always be a problem. Controlling and the addition of safety masks will help the health. Good luck.

 

[Curly]

From post 28
"Now, I'm not quite sure I understand this notion about only counting the wyes if it changes direction? What exactly do you mean by change direction?"

By that I mean if you go along your main line through wyes you don't count them if the air is going straight. If the air takes a wye to branch off to a machine mid-room then you count it because it took a 45º turn. That is with the understanding that the branch is closed with a blast gate and knowing there is a slight loss due to turbulence as the air passes over the opening. Closer the blast gate is to the wye the better but then you have to be able to reach it.

From post 29
"Hmm, another question. The CV systems make specific note of the fact that the filters are off of a 90 degree turn. I am not sure if that is something I need to account for, as another turn in the entire system? I am honestly not sure. On that side of the impeller, the pressure would be positive, rather than negative...but maybe that 90 degree turn still has an impact on the overall system?"

CV's model numbers is the airflow with the elbow and 2 filters. A CV-1700 having 1700cfm, a CV-1950 having 1950cfm. Until the filters clog up they are not a factor. Commercial DC's have manometers that measure the filter side of the cyclone and when they have a 3" or 4" (from memory) signal that cleaning is needed or they start the automatic cleaning cycle, shakers or reverse blasts of compressed air. If you put your own manometer, water tube type will do, on the filter side and when you get a couple inches difference from the new state clean them. best as I said before considering your reactions to dust is to vent outside when the weather permits and use filters when it doesn't.

The Aussies have the best dust information in their forum around. After you finish with Bill's site read the Sticky Threads at the top and then any of the posts over the last 5 years or so that catch your eye. There is a lot of good stuff on measuring, ducting, venting, sound enclosing and baffling the exhaust noise. Unfortunately for them there is no CV presence in Australia anymore as the costs to ship became too high over the last few years. They have a lot pertaining to them. https://www.woodworkforums.com/f200

 

[Curly]

Forgot to mention floor sweeps are not a good ideas because the act of sweeping stirs up a lot of dust. Better to vacuum the dust off the floor with a HEPA rated vacuum.

 

[jrista]

A way to look at things is if the dust collector has enough suction to collect large particles or chips it has enough power to collect whatever dust is present at the opening. Plain and simple.

Have YOU read what Bill Pentz wrote? What you state here flies directly in the face of his entire site. You should re-read it. I hate to say it but you are following debunked science here, and this is, ironically, exactly the problem Pentz is trying to fix with his web site.

Suction of air has a 12x larger factor of falloff than simple linear inverse square falloff, due to the fact that suction occurs in all directions around the hood. Due to this fact, suction of fine dust is a significantly more challenging problem than suction of lager dust particles or chips. Most of the preliminary stuff on his site, is trying to make the reader understand that FINE dust (that with the greatest health risk), will NOT get collected if you follow the reasoning you just shared here. Collecting large particles or chips, is NOT the same as capturing fine dust. Fine dust, BTW, or true wood dust, is by definition invisible to the naked eye, which makes it particularly insideous. This is something else he covers on his site...that most DCs on the market will take care of the chips and coarse dust, the stuff you can "see", leaving you with what generally appears to be a "clean" shop, all the while the air can suspend fine wood dust effectively indefinitely, and even when it settles, the slightest breeze will kick it back up into the atmosphere again. This stuff is invisible, but is of the greatest concern health wise, as its what penetrates deepest into the lungs, and can get absorbed directly into the bloodstream. Its razor sharp, nasty stuff. (READ HIS SITE!)

Fine dust gets deflected by the smallest of forces, which can pull it away from the dust collection inlet before the suction captures it, which doesn't happen with the larger particles. For the DC to fully collect all the dust, including the most dangerous from a health standpoint, you need significantly higher CFM than most of the "studies" have demonstrated for so many decades. That is effectively the entire point of his site, to educate people to this fact, and help them understand that 350-400CFM will plain and simply not collect the fine dust, thus making your "dust collector" just a "chip and shavings collector", and how to actually collect the majority of dangerous wood dust with a proper DC.

His site, and several other writings of his, are very plainly clear: At a MINIMUM, you need ~1000CFM @ 4000FPM with a 7" hood and duct, in order to collect fine dust. Technically speaking, the duct and hood actually has to be 6.7" in diameter, and since dust collectors are usually 6" or 8", you need one of those. A 6" duct is not quite going to give you 1000CFM, although it gets pretty close. Unless you are using a very powerful dust collector, 8" ducting will usually not meet the bare minimum 4000FPM requirement (the CV1700 comes in a bit over 2000FPM @ 8" when I configure it for my needs), and won't actually move particles all the way to the DC.

 

[jrista]

Now you mentioned a couple times about PVC and static and grounding. This is a debunked myth within a home workshop. You will not produce enough static within or outside a pvc pipe to cause a arc.

So I have to dispute this as well. I currently use 2.5" PCV tubing. I've had plenty of static buildup on this, and have touched it when its charged and received visible arcs to my fingers and some nasty pain. I've had the same problem with my shop vacs hoses, although not as severe. This isn't just some myth...I've had numb then painful fingers for hours as a result of the static discharge that occurs when I've touched a highly charged DC duct in my own shop.

I'm not really a believer in "This myth has been debunked" as time and time again, I either find fundamental flaws in the studies (i.e. the video that Pete linked earlier, was a FOUNDATIONALLY FLAWED test, and is EXACTLY the reason why I don't trust studies that show that static buildup isn't a problem), or the studies don't seem to understand what actually carries either the static charge itself, or what actually CONDUCTS electricity WHEN there is a static charge built up. The PVC doesn't conduct anything, of course. The built up charge itself on the PVC, is what actually does the conducting. The charge produces an electric field. If you should understand anything about electricity, you should understand that it is not actually the movement of charged particles that actually moves electric energy...it is the field itself, that holds electrical energy, and electric and magnetic fields together that convey the energy. This is true for any electrical system:

For anyone working with charged systems, understanding how energy is actually conveyed, is important. For a DC, static electricity, since it creates an electric field (i.e. like a battery), should be of concern. All you have to do is complete the circuit from that "battery", to FEEL the consequences of that charge build up. Doesn't matter that its built up on a PCV pipe...the PCV is immaterial here. The charge itself, is the problem. Its effectively a battery, it is a store of electrical energy. A single finger touch is going to complete a small circuit and will usually result in a small arc. A whole hand, could discharge a lot more energy at once. In either case, if you look into it, the smallest energy discharge that CAN ignite wood dust suspended in air (not that it always will), is a mere 1mJ (millijoule), while more on average it might take 20-30mJ to ignite fine dust at the right concentrations (this is actually similar to flour, which can also cause dust explosions). The average static discharge to a finger/hand, is around 60mJ! I have a nat gas line running high up on one of my walls. I intend to take no risks. To me, even if they are low, fire is IMO one of the worst disasters in a woodshop, especially if that shop is attached to your home.

Anyone ever hear that old "safety" adage: Safety is a CHOICE, first and foremost?

 

[jttheclockman]

Have YOU read what Bill Pentz wrote? What you state here flies directly in the face of his entire site. You should re-read it. I hate to say it but you are following debunked science here, and this is, ironically, exactly the problem Pentz is trying to fix with his web site.

Suction of air has a 12x larger factor of falloff than simple linear inverse square falloff, due to the fact that suction occurs in all directions around the hood. Due to this fact, suction of dine dust is a significantly more challenging problem than suction of lager dust particles or chips. Most of the preliminary stuff on his site, is trying to make the reader understand that FINE dust (that with the greatest health risk), will NOT get collected if you follow the reasoning you just shared here. Collecting large particles or chips, is NOT the same as capturing fine dust. Fine dust, BTW, or true wood dust, is by definition invisible to the naked eye, which makes it particularly insideous. This is something else he covers on his site...that most DCs on the market will take care of the chips and coarse dust, the stuff you can "see", leaving you with what generally appears to be a "clean" shop, all the while the air can suspend fine wood dust effectively indefinitely, and even when it settles, the slightest breeze will kick it back up into the atmosphere again. This stuff is invisible, but is of the greatest concern health wise, as its what penetrates deepest into the lungs, and can get absorbed directly into the bloodstream. Its razor sharp, nasty stuff. (READ HIS SITE!)

Fine dust gets deflected by the smallest of forces, which can pull it away from the dust collection inlet before the suction captures it, which doesn't happen with the larger particles. For the DC to fully collect all the dust, including the most dangerous from a health standpoint, you need significantly higher CFM than most of the "studies" have demonstrated for so many decades. That is effectively the entire point of his site, to educate people to this fact, and help them understand that 350-400CFM will plain and simply not collect the fine dust, thus making your "dust collector" just a "chip and shavings collector", and how to actually collect the majority of dangerous wood dust with a proper DC.

His site, and several other writings of his, are very plainly clear: At a MINIMUM, you need 1000CFM @ 4000FPM with a 7" hood and duct, in order to collect fine dust. Technically speaking, the duct and hood actually has to be 6.7" in diameter, and since dust collectors are usually 6" or 8", you need one of those. A 6" duct is not quite going to give you 1000CFM, although it gets pretty close. Unless you are using a very powerful dust collector, 8" ducting will usually not meet the bare minimum 4000FPM requirement (the CV1700 comes in a bit over 2000FPM @ 8" when I configure it for my needs), and won't actually move particles all the way to the DC.

Jon I am not trying to debunk what he is saying or whatever anyone else is saying. I do not need to read what Bill is saying or what anyone else is saying. I have my duct system setup that works for me. I looked into systems when I was building but again came to the same conclusions I tried conveying to you now. What I am saying is you are spending so much time trying to make the perfect dust collection system that it will NEVER happen. It just can't. There are too many other factors than a dust collector picking up dust from a tool and I tried to lay them out to you but you are not listening so have at it. Every breath you take in from anywhere in the world you are inhaling contaminants that are not good for your lungs. The very carpet you walk on, the car you drive and all those plastics you drink from and the list goes on. We as woodworkers face extra contaminants from materials we cut, materials we finish with, materials we sand with and this list can go on forever. I understand you are attempting to make your little workshop as safe as possible from airborne dust. This is great but again you will have to enclose every tool you use that cuts and sands or else all the duct systems you build will not do what you want. Now if that is debunking then so be it . It is the nature of the beast. To combat this the use of air cleaners as well as dust masks with OSHA approval ratings is the most pure attack you can do or any woodworker can do. Believe me or not I do not care, others can argue also but prove to me you are collecting all dust particles with any dust collector built and I will eat my words. The moment you get dust no matter what size on that very floor you walk on in your shop you started a chain reaction of that dust being released back into the air and the cycles begins again and the contaminants are there to get in your lungs. I am done with this discussion so again I wish you luck in your quest. and I do mean it.

 

[jttheclockman]

So I have to dispute this as well. I currently use 2.5" PCV tubing. I've had plenty of static buildup on this, and have touched it when its charged and received visible arcs to my fingers and some nasty pain. I've had the same problem with my shop vacs hoses, although not as severe. This isn't just some myth...I've had numb then painful fingers for hours as a result of the static discharge that occurs when I've touched a highly charged DC duct in my own shop.

I'm not really a believer in "This myth has been debunked" as time and time again, I either find fundamental flaws in the studies (i.e. the video that Pete linked earlier, was a FOUNDATIONALLY FLAWED test, and is EXACTLY the reason why I don't trust studies that show that static buildup isn't a problem), or the studies don't seem to understand what actually carries either the static charge itself, or what actually CONDUCTS electricity WHEN there is a static charge built up. The PVC doesn't conduct anything, of course. The built up charge itself on the PVC, is what actually does the conducting. The charge produces an electric field. If you should understand anything about electricity, you should understand that it is not actually the movement of charged particles that actually moves electric energy...it is the field itself, that holds electrical energy, and electric and magnetic fields together that convey the energy. This is true for any electrical system:

For anyone working with charged systems, understanding how energy is actually conveyed, is important. For a DC, static electricity, since it creates an electric field (i.e. like a battery), should be of concern. All you have to do is complete the circuit from that "battery", to FEEL the consequences of that charge build up. Doesn't matter that its built up on a PCV pipe...the PCV is immaterial here. The charge itself, is the problem. Its effectively a battery, it is a store of electrical energy. A single finger touch is going to complete a small circuit and will usually result in a small arc. A whole hand, could discharge a lot more energy at once. In either case, if you look into it, the smallest energy discharge that CAN ignite wood dust suspended in air (not that it always will), is a mere 1mJ (millijoule), while more on average it might take 20-30mJ to ignite fine dust at the right concentrations (this is actually similar to flour, which can also cause dust explosions). The average static discharge to a finger/hand, is around 60mJ! I have a nat gas line running high up on one of my walls. I intend to take no risks. To me, even if they are low, fire is IMO one of the worst disasters in a woodshop, especially if that shop is attached to your home.

Anyone ever hear that old "safety" adage: Safety is a CHOICE, first and foremost?

Oh I am not going down this rabbit hole with you. Again do what you feel is necessary to make you feel safe. Within every statement context can be deployed to turn things around in the way you want to read itGood luck.

By the way my point about that static thing was people wrapping pvc with copper wires is not stopping static charge. That was my main point. All those studies and numbers in what you wrote are probably true . No argument. This therory about wrapping a pvc pipe with copper wire is what I was calling a debunked therory.

 

[jrista]

Jon I am not trying to debunk what he is saying or whatever anyone else is saying. What I am saying is you are spending so much time trying to make the perfect dust collection system that it will NEVER happen. It just can't. There are too many other factors than a dust collector picking up dust from a tool and I tried to lay them out to you but you are not listening so have at it. Every breath you take in from anywhere in the world you are inhaling contaminants that are not good for your lungs. The very carpet you walk on, the car you drive and all those plastics you drink from and the list goes on. We as woodworkers face extra contaminants from materials we cut, materials we finish with, materials we sand with and this list can go on forever. I understand you are attempting to make your little workshop as safe as possible from airborne dust. This is great but again you will have to enclose every tool you use that cuts and sands or else all the duct systems you build will not do what you want. Now if that is debunking then so be it . It is the nature of the beast. To combat this the use of air cleaners as well as dust masks with OSHA approval ratings is the most pure attack you can do or any woodworker can do. Believe me or not I do not care, others can argue also but prove to me you are collecting all dust particles with any dust collector built and I will eat my words. The moment you get dust no matter what size on that very floor you walk on in your shop you started a chain reaction of that dust being released back into the air and the cycles begins again and the contaminants are there to get in your lungs. I am done with this discussion so again I wish you luck in your quest. and I do mean it.

It is not that I am not reading. I am. It is that I disagree with what you are saying. You linked me Bill Pentz site. I read it (or have read a lot of it now). What is is saying, and what you are saying, are distinctly different. I find that rather ironic, given you linked his site. I guess I'm one to call out inconsistencies like that when I see them.

He is quite clear that 1000CFM collection capability AT THE TOOL, does matter. It collects around 15% more dust according to testing, the ultra fine dust that hangs around in the atmosphere. I think you are sharing some bad information, the same kind of bad information I've been sifting through for weeks, and the same kind of bad information that leads to a lot of confusion. Worse, the same false information that I think may give many shop owners a false sense of health safety (it certainly did to me until a couple days ago!!) I mean, I honestly thank you (and Pete!) for sharing Bill Pentz site, as it has been immensely informative, and has cleared up a lot of questions. I'm honestly quite confused by why you are now sharing exactly the FLAWED thinking he is trying to warn people away from on his site.

FWIW I'm not looking to build the perfect system. I never said that. I am, however, looking to build a system that will actually limit the health risks, as well as the negative health episodes that I REGULARLY have with my shop now. Pete asked it earlier in the thread, am I actually interested in protecting my health. That really spurred me on to reconsider what I thought I knew, and really, thoroughly read Pentz site (I've read bits and pieces before, never started at the beginning though, and was missing a lot of what he is trying to do.) Based on the link you shared, and not out of some desire to build a perfect system, I now strongly believe I need a DC that can actually suck enough air to deliver 1000CFM to the machines I use, over the distances in my shop, with the number of turns I expect to need. I want a system that WILL actually capture AND RETAIN the dust it collects.

Bill covers quite a bit about how mainstream DC systems are actually quite insufficient from the standpoint of actually retaining all the dust they collect, or even being capable of capturing it all in the first place. Now, he was sympathetic to the plight of mainstream DC manufacturers, and his site was written back in the early 2000s. I know that some things have changed since then, however, so much hasn't changed at all. There is GREAT risk being imposed on home shop owners, with all of these "bag" collectors that only filter down to 30 microns!! They proclaim to improve safety, but do nothing of the sort, and worse...convey a FALSE sense of safety and health benefit on users of such systems. Even a "good" cyclone DC with a "1 micron" filter (very misleading, unless you are careful about checking the capture percentages, which are sometimes pitifully in the 80% range, meaning a huge amount of fine dust is leaking back into your air!!) is both significantly underpowered (3HP with just a 12" impeller on a Cyclone is only going to move chips and coarse dust and won't collect the fine dust at all...even though it will give your shop a shiny clean look to it.) Back in 2000, testing showed that 1,1.5, 2 and 3 hp DCs were actually all moving the same amount of air! This is something that has possibly been remedied to a degree today (probably depends on the manufacturer), but from a physics standpoint, a 12" impeller can only move so much air, regardless of how strong the motor is... The Jet, Laguna, Grizzly, etc. units I was looking at, all of which have a rotating bar you can use to knock off dust from the filter into a collection bag...seem really great, super convenient. In fact, those bars that rub against the pleats in those filters are actually damaging them, and can easily enough create holes that allow more and more dust to just blow right through the system, pumping the fine dust back into the air of the shop. I actually wondered about this while I was standing in a woodcraft, playing with those very cleaning arms... Legit wondered if that would destroy the filter.

That site has been incredibly illuminating and informative, and has been one of the best sources of education on the subject I've come across. I very nearly put thousands of dollars into a DC system, that most likely would not have saved me from any of the health ailments I suffer when exposed to very small amounts of wood dust. I'm still reading, don't yet have all the knowledge he has to share, which I'm sure will continue to inform my decisions. I have yet to figure out exactly what to do from a ducting standpoint, still need to make sure a 1700CFM unit with a 16" impeller is going to work (sounds like it, if I do the ducting right, but I have some limitations in just how I'm able to route the ducting, so we'll see.) I certainly don't want to invest any amount of money in a system that isn't going to keep me from suffering the nasal and breathing issues I keep suffering. I'm tired of that misery. This isn't just trying to protect my shop from an explosion, in fact that's the lesser of my concerns. I regularly SUFFER from the effects wood dust has on me, my body. I'm tired of suffering. THAT is the primary goal here. (FWIW, I drink out of metal or glass, never out of plastic...maybe occasionally out of a cardboard carton when it comes to coconut milk, the only milk I drink.)

He does talk about dust collection hoods, and I haven't gotten into the depths of that just yet, but I already knew that the kind of hood you use also matters. I have never been under the illusion that I'd be capturing 100% of every dust particle generated, either...and I've mentioned the other measures I have and use to cover collecting the remnant that isn't picked up by the DC at the tool. My tools are primarily lathe and bandsaw, too. I currently do not have a table saw, but I intend to plan ahead so that when the come comes that I do, I'm able to collect dust from it effectively as well (and I've been looking into how people maximize dust collection with a table saw...there are many tactics that can be employed to maximize dust collection and minimize escaped dust, even with a table saw.)

FWIW, I'm not trying to chase you away from the discussion/debate. I am of the mindset that debates in threads like these bring hard facts to the surface, and can benefit all readers. You are free to bow out. I just see some inconsistencies, and can't help but point them out. Having read Bill's site, I am not sure I trust OSHA or any other governmental agency, certainly don't trust manufacturers (some things have improved in 20 years, a lot doesn't seem to have changed at all). Reasons why are all in his site.

I hope other readers of this thread, are reading that site. I know some of you aren't concerned about wood dust. I am, due to my own personal experiences and how it has directly affected my health so far. I hope some of you are as well...the potential long-term consequences of breathing fine wood dust can be devastating. Some may not experience it until they are into their 50s or beyond, others may experience symptoms more readily. I certainly experience them quite readily, and it is legitimately miserable, constantly having to suck in air because you can't breath through your nose, or constantly have a cough because you were exposed to just a small amount of dust when you weren't thinking about it. I've had a decent break from woodworking for a while here. I've been able to breathe well for the last few months. It is truly AMAZING what a difference it makes, to the quality of life I have. I don't want to be back in the same boat I've been in for the last few years, sucking in air, struggling to breathe. I have had allergies my whole life, also been doing allergy shots the last few years. For most of my life, I've suffered the inability to breathe well. Now that I've experience GOOD breathing...I'm not willing to give it up. I wonder how many other readers, may simply not know what it is like to breath clearly, without pain in your throat or chest, constantly stuffed up nasal passages, that near-constant flu-like feeling. If you haven't...well, I hope you are reading, and I hope you consider: You CAN experience better breathing, and it WILL have a hugely positive impact to the quality of your life...

Well, with that....I have other things to get to...

 

[jrista]

From post 28
"Now, I'm not quite sure I understand this notion about only counting the wyes if it changes direction? What exactly do you mean by change direction?"

By that I mean if you go along your main line through wyes you don't count them if the air is going straight. If the air takes a wye to branch off to a machine mid-room then you count it because it took a 45º turn. That is with the understanding that the branch is closed with a blast gate and knowing there is a slight loss due to turbulence as the air passes over the opening. Closer the blast gate is to the wye the better but then you have to be able to reach it.

From post 29
"Hmm, another question. The CV systems make specific note of the fact that the filters are off of a 90 degree turn. I am not sure if that is something I need to account for, as another turn in the entire system? I am honestly not sure. On that side of the impeller, the pressure would be positive, rather than negative...but maybe that 90 degree turn still has an impact on the overall system?"

CV's model numbers is the airflow with the elbow and 2 filters. A CV-1700 having 1700cfm, a CV-1950 having 1950cfm. Until the filters clog up they are not a factor. Commercial DC's have manometers that measure the filter side of the cyclone and when they have a 3" or 4" (from memory) signal that cleaning is needed or they start the automatic cleaning cycle, shakers or reverse blasts of compressed air. If you put your own manometer, water tube type will do, on the filter side and when you get a couple inches difference from the new state clean them. best as I said before considering your reactions to dust is to vent outside when the weather permits and use filters when it doesn't.

The Aussies have the best dust information in their forum around. After you finish with Bill's site read the Sticky Threads at the top and then any of the posts over the last 5 years or so that catch your eye. There is a lot of good stuff on measuring, ducting, venting, sound enclosing and baffling the exhaust noise. Unfortunately for them there is no CV presence in Australia anymore as the costs to ship became too high over the last few years. They have a lot pertaining to them. https://www.woodworkforums.com/f200

Thanks for the info, and for the Aussie forum link. I still have plenty of reading to do. I have much, much clearer understanding of what is necessary here, now, though. For me, first and foremost, is the health issue. I've suffered from wood dust. This is the year I intend to make this hobby a business, and I'm getting back into it all right now. I intend NOT to suffer from wood dust as I have been the last few years.

I understand the difference between what 350-400CFM will do, and 1000CFM. With the CV1700, it sounds like I should be able to get over 5000FPM airflow, which should get me pretty darn close to 1000CFM with a 6" duct. I just need to figure out if I can make that kind of a DC work in my shop...

Regarding a manometer. How easy is it to get one of those integrated into your own system? I have actually wondered about cleaning the filters. CV's site recommends blowing the filter out. I understand that now. At first I was thinking it would be a real pain in the butt, and whether it would be possible to add one of those levered arms to mechanically knock dust off the pleats of the filters. However I was always concerned about whether that might damage the filter, even when looking at the Jet (and others). That cleaning arm seems to be fairly common. Reading Bill's site, its clear to me now that I was not just missing something, they actually do damage the filter. I am now wondering how often I might have to clean the 600 square feet (I also understand why this is necessary now, thanks to Bill's site) of fine filter the CV units come with, and if a manometer can help me determine that, then that would be a useful addition.